Just bought a "Ring 21" Powerboat, what is the maximum safe hp outboard it can take?

Mid 80's restoration project without a builders plate right? Most Ring 21's are.Yeah, we had the same problem. I've seen everything from 140-275 sometimes twin engines. Deep V racing hull tends to rail-walk in calm water especially on higher hp. We settled for a 250 to play it safe,good all-rounder but hasn't hit the 80mph yet. Guess this is really a question for a Marine Architect not the likes of julianjoe who isn't really the sharpest tool in the box and should stick to licking windows at McDonald's. Hope I was of some help, have fun!